This invention relates generally to forming of glass fiber composites, as are used in high-efficiency air filtration; and more particularly the invention concerns a method of effecting controlled filtering capacity of two layers of fibers, of different sizes, by passage of air through the two layers, to control overall thickness.
There is need for longer-life filters capable of efficiently filtering particulate from gas streams, and there is need for efficient, effective methods of producing such filters. There is also need for preventing escape of smaller diameter glass fibers from a fibrous mat. The disclosure of U.S. Pat. No. 3,690,852, incorporated herein by reference, concerns production of a filter comprising two layers of fibers of different sizes. The present invention improves upon the methods described in that patent, as will be seen.